-Single-parameters band model -Band model compute transmittance averaged over a spectral band (band model parameters every 5 cm-1) -20 cm-1 resolution from 0 to 50,000 cm-1 -Does not fully represent the correct T dependence -Three classes of atmospheric gases -Water vapor, ozone, and uniformly mixed gases -Atmosphere is divided into 32 layers -0 to 100,000 km altitude -Layer thickness varies from 1 km to 30 km -Characteristics of each layer determined by inputs standard models of various regions and seasons -Calculation based on -LOWTRAN band model -Molecular continuum absorption -Molecular scattering -Aerosol absorption and scattering models -Includes -Atmospheric self-emission -Solar and/or lunar radiance single scattered into the path -Direct solar irradiance through a slant path to space -Multiple scattered solar and/or self-emission radiance into the path